There is no special ceremony for this conversion to Islam, except a public declaration of the above.

Once a person becomes a Muslim, he cannot be declared a non-Muslim until he himself renounces Islam in clear terms. There is a verse of the Holy Quran which tells Muslims not to call a person a non-Muslim when he offers you a salutation in the Islamic way, and there are Hadith (Traditions) of the Holy Prophet Muhammad, peace and blessings of Allah be upon him, which declare that if a person has one out of a hundred reasons to be known as a Muslim and ninety-nine reasons for being a non-Muslim, he should not be called a non-Muslim.

Then again there is a Hadith which tells us that the Holy Prophet Muhammad, peace be upon him, said that whosoever prays our way (man salla salaatana) and adheres to our Qibla (wastaqbala qiblatana) and eats our slaughtered meat (wa aqala zabeehatana) he is a Muslim and Allah and Allah’s Messenger vouchsafe for him.

Now in the presence of such clear injunctions whosoever calls a Muslim a non-Muslim is clearly violating the Quran and Sunnah and his pronouncements clearly amount to telling us that such a person in fact likes to give preference to his personal views over the injunctions of the Quran and Sunnah. Such an idiocy merits the dislike of all righteous Muslims who believe in the supremacy of the Quran and Sunnah to all other things.